This invention relates to the projection of images with a controlled amount of distortion. More particularly, this invention relates to the projection of an image from a projection point that differs from the camera viewpoint from which it was recorded, to be viewed by a viewer from a viewer viewpoint substantially identical to the camera viewpoint.
In certain situations, it is desirable to project wide angle images in front of an audience onto a distorted--e.g., curved--screen. For example, in an amusement park "dark ride," a viewer or "guest," seated in a moving vehicle, is transported through a fantastic or magical world within a darkened or "light-controlled" building. An example of such a ride is a fun house, in which a guest seated in a car riding on track travels through sets depicting various vistas, such as a dungeon populated with various characters, followed by a cemetery from which ghosts are rising from the ground, and so forth. In such dark rides, viewers may be transported quickly past such scenes in limited space, yet the image sought to be presented to the viewer is one of a vast expanse, possibly stretching to the horizon or, in an outer space-type or other fantastic-type attraction, to infinity.
To achieve such an illusion, the scene to be presented to the user can be recorded (whether by filming photographically or electronically, or by animating, or by generating computer graphics) using a lens (a true optical lens in the case of photographic or electronic filming, or an applied distortion or transfer function in the case of animation or computer graphics) that transforms a wide view onto a small surface. One such lens in the optical domain might be a wide-angle or "fisheye" lens. The distorted image could then be played back through an appropriate projection lens, which may be the same or similar to the recording lens, onto a screen which may also be distorted. For example, to achieve the illusion of a vast expanse an appropriately curved screen might be used.
However, such techniques result in distortion to the viewer unless the various distortions can be cancelled out by each other or otherwise. One way to compensate for some of such distortions is to place the camera at the same point relative to the subject at which the viewer's eye will ultimately be relative to the image of the subject, moving it if necessary in the case of moving ride. However, in the case of a moving ride, or a moving image, it is not possible to place the projector at that point unless the projector is also allowed to move. Arranging for such movement, such as placing the projector on the ride vehicle, is complex and expensive, requiring, at the very least, a separate projector for each vehicle. Placing the projector on the vehicle subjects the projector to possible vibration-induced damage, and at the same time increases the difficulty of access for maintenance purposes. Even if the viewers remain stationary, the projector might have to be placed on a different axis to avoid casting shadows of the viewers or their chairs on the screen.
Similar considerations arise in the case of a simulator-type ride where the viewer is supposed to believe he is looking out to infinity (or at least to the horizon). If the distortions are not corrected for, the viewer will realize that the screen is a finite (and small) distance away. The option of placing the projector on the simulator platform is even less attractive than that of placing it on a moving ride vehicle because it is subject to even more violent motion, in addition to the other reasons noted above.
There are known techniques for dealing with distortions induced by recording of images. However, such techniques are incapable of dealing with situations in which different distortions of the image are applied at different points in the system--e.g., at the camera, at the screen and at the projector--and at the same time dealing with a sequential series of images representing motion.
Accordingly, it would be desirable to be able to project an image, taken from a particular point of view, onto a screen, especially a curved wide angle screen, from a different point of view, to be viewed from the original point of view, without distortion.